The invention concerns heating of materials, and more particularly heating with radio frequency (RF) energy that can be applied to process flows. In particular, this disclosure concerns an advantageous method for RF heating of materials that are susceptible of heating by RF energy by electric dissipation, magnetic dissipation, electrical conductivity and by a combination of two or more of them. In particular, this invention provides a method and apparatus for heating mixtures containing bituminous ore, oil sands, oil shale, tar sands, or heavy oil during processing after extraction from geologic deposits.
Bituminous ore, oil sands, tar sands, and heavy oil are typically found as naturally occurring mixtures of sand or clay and dense and viscous petroleum. Recently, due to depletion of the world's oil reserves, higher oil prices, and increases in demand, efforts have been made to extract and refine these types of petroleum ore as an alternative petroleum source. Because of the high viscosity of bituminous ore, oil sands, oil shale, tar sands, and heavy oil, however, the drilling and refinement methods used in extracting standard crude oil are typically not available. Therefore, bituminous ore, oil sands, oil shale, tar sands, and heavy oil are typically extracted by strip mining, or from a well in which viscosity of the material to be removed is reduced by heating with steam or by combining with solvents so that the material can be pumped from the well.
Material extracted from these deposits is viscous, solid or semisolid and does not flow easily at normal temperatures making transportation and processing difficult and expensive. Such material is typically heated during processing to separate oil sands, oil shale, tar sands, or heavy oil into more viscous bitumen crude oil, and to distill, crack, or refine the bitumen crude oil into usable petroleum products.
Conventional methods of heating bituminous ore, oil sands, tar sands, and heavy oil suffer from many drawbacks. For example, the conventional methods typically add a large amount of water to the materials and require a large amount of energy. Conventional heating methods do not heat material uniformly or rapidly which limits processing of bituminous ore, oil sands, oil shale, tar sands, and heavy oil. For both environmental reasons and efficiency/cost reasons it is advantageous to reduce or eliminate the amount of water used in processing bituminous ore, oil sands, oil shale, tar sands, and heavy oil, and to provide a method of heating that is efficient and environmentally friendly and that is suitable for post-excavation processing of the bitumen, oil sands, oil shale, tar sands, and heavy oil.
RF heating is heating by exposure to RF energy. The nature and suitability of RF heating depends on several factors. RF energy is accepted by most materials but the degree to which a material is susceptible to heating by RF energy varies widely. RF heating of a material depends on the frequency of the RF electromagnetic energy, intensity of the RF energy, proximity to the source of the RF energy, conductivity of the material to be heated, and whether the material to be heated is magnetic or non-magnetic.
RF heating has not replaced conventional methods of heating petroleum ore such as bituminous ore, oil sands, tar sands, and heavy oil. One reason that RF heating has not been more widely applied to heating of hydrocarbon material in petroleum ore is that it does not heat readily when exposed to RF energy. Petroleum ore possesses low dielectric dissipation factors (∈″), low (or zero) magnetic dissipation factors (μ″), and low or zero conductivity.